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Dual Port SAS cables.

C

Computurd

Gawd
Joined
Dec 19, 2008
Messages
956
hey guys here is the deal, i have some dual port SAS SSD, the Pliant Lightning LS 300S, and the enclosure i have is not dual port capable.
Despite the fact that i specifically stated the requirement that it needs to be dual port capable.
I am a dual port SAS noob, so i need to know what kind of cables i would need to go from the raid card directly to the devices. 8087 to Dual Port SAS Capable cables....with no enclosure.
any ideas?
 
I dunno if such things exist....

Dual port, is usually for dual controllers....ie two ways to get to a drive

Have a looksee at the ACTUAL SAS connection, the little bump that block them from connecting to SATA is where the extra port is (ie more pins)

So it's only going to work connected to a dual port SAS backplane I would imagine

.
 
Stanza33 is correct, dual port provides a secondary controller + necessary connections. A single 8087 to dual port cable simply doesn't exist because that would create two connections to a single controller. Were you thinking of the SAS 2.0 dual link feature? AFAIK, that's only used for connections between controllers and expanders.
 
That completely defeats the point of having dual ports on a drive.
Click to expand...

why? well in a conventional sense, yes. but for drives that you can use both ports for the same device on the same controller, WidePort, it is perfectly viable.
Not using the dual ports in failover/load balancing in this testing. for these tests its all about performance :)
These puppies need I/O
http://www.shop.datastoragesys.com/...0-Enterprise-Flash-Drive-PT-LS0300-00-SGL.htm
2011-06-2322-13-15857.jpg
 
Ummm no not really.

If you have a look @ SAS drives you will notice each one has a different SAS ADDRESS... ie like each network card has a different MAC ADDRESS

Then have a look @ Dual port drives..... they have 2 different SAS Addresses to reflect the different SAS ports

I would imagine connecting one controller via two cables to the same drive is going to cause some interesting problems.

either the controller is going to think there is TWO seperate drives and try and access both of them at the same time.... or actually I have no idea whats going to happen.

Plug it in and let us know if any magic black smoke escapes:D
 
Computurd said:
http://www.computercablesource.com/...data--power-for-dual-port-sas-drive-2013.html
Click to expand...

What is the point of that link?

Unless you actually have one of those cables in your hot little hands..... just looks to me like a SFF-8087 to SFF-8482 2 x SAS.... instead of the normal SFF-8087 to SFF-8482 4 x SAS/SATA breakout cables you can buy.

Seeing as the photo shows only a P1 cable attached to one end.... and not say P1 on the left side and P2 on the right side then the power.... I would be suspicious that they are just normal cables... nothing dual port about them. (tho they could be somehow wired as such physically)...

That is, the SFF-8087 has 4 ports yes.... so take port 1 and join that to the normal SATA side of the SFF-8482. then Join Port 2 up to the 2nd SAS port on the SFF-8482

Do the same for port 3 and 4... and yes you would have a DUAL PORT cable as such....

Even the description of the link you posted (which I always take with a grain of salt when used to describe SATA/SAS cables) says

SAS Cable - 1 Meter Internal Mini SAS 36 to 2 SAS 29 Data & Power - For Dual Port SAS Drive

If I changed that description to

SAS Cable - 1 Meter Internal Mini SAS 36 to 2 SAS 29 Data & Power

I think thats what it would actually be

in which case...Save your $43 and buy these instead
http://www.ebay.com.au/itm/LSI-3Ware-SAS-cable-SFF-8087-SFF-8482-power-x4-SAS-/130511029075?pt=LH_DefaultDomain_0&hash=item1e63104353

and you will have double the connections;)

.
 
these devices have a wideport mode that allows link aggregation.
this isnt standard usage here...these things gain speed using two ports...
pliant-Copy.png



and the wideport mode works differently than you might be accustomed to. would those cables that you linked do the wideport mode on these devices? as you can see they take up two channels for each device. so you would need a specialized cable i believe.
plaint2-Copy.png
 
Then have a look @ Dual port drives..... they have 2 different SAS Addresses to reflect the different SAS ports
Click to expand...

this is actually how it is supposed to work with these devices. these arent your grandmas SSDs.
each port is a seperate DRIVE.
 
Ahhh, now that explains a bit more.

Anyways, seems I was wrong and THAT cable is the one needed. (but still won't do what you want)
Have a read here, and also maybe contact the person who wrote this as to how he ended up configured....
http://sqlserverio.com/2011/05/23/pliant-technology-enterprise-flash-drives-for-your-sql-server-part-1/

Seems like windows saw these as TWO drives each.... (which makes sense like I described how the cable could have been configured).

So the drives each come up as an MPIO configurable device. Hence the Dual ports.. Hence the Dual SAS Addresses etc. Both coming from the same controller.

I still don't see the benifit of it... As MPIO is for redundancy... so if you controller fails you still have a path to your DATA (Drive).

Using one controller sort of defeits the purpose really.

If you are looking to use both ports to increase speed... I don't think that will happen.

Failover
No load balancing is performed. The application specifies a primary path and a set of standby paths. The primary path is used for processing device requests. If the primary path fails, one of the standby paths is used. Standby paths must be listed in decreasing order of preference (the most preferred path first).


Failback
Failback is the ability to dedicate I/O to a preferred path whenever it is functioning. If the preferred path fails, I/O is directed to an alternate path until function is restored to the preferred path, but I/O automatically switches back to the preferred path when function is restored.


Round-robin
The DSM uses all available paths for I/O in a balanced, round-robin fashion.

ie
Just think networking and having 2 x lan ports..... bonding 2 x 1gig doesn't magically get you a 2gig port....if gives you 2 x paths of 1gig each

If you want SPEED, I would suggest just using normal SFF-8482 I linked too and using say ZFS to pool the drives into one VDEV (no mirrors or RAIDZ)

That will effectivly give you a RAID 0 across all the drives using one port on each.

And if you do want some sort of safety net enable copies=2 or just use Mirrors and lose half the capacity.

With the speeds Pliant rate these @ you are going to have some pretty speedy storage either way:cool:
 
Computurd said:
this is actually how it is supposed to work with these devices. these arent your grandmas SSDs.
each port is a seperate DRIVE.
Click to expand...

I didn't know grandma had SSDs. :D

Great info guys, can't wait to try some of this out.
 
@ stanza.
these devices are designed to be used this way.They arent some cheap little thing that isnt going to perform how they advertise it. They are guarantied for 5 years and unlimited writes. in single port mode you simply do not get the full performance.

If you are looking to use both ports to increase speed... I don't think that will happen.
Click to expand...
They are configured to use dual port. Dual port on the SAS HDD that you are familiar with do not benefit from the enhanced throughput, as they are not fast enough to deliver.
These however, are desgned as such. there are 3 PCB inside of these 3.5 inch form factor EFD (Enterprise Flash Device).
they are literally configured to be several drives in one. they CAN be used for failover, but are more tailored for MPIO & Wideport, for higher speeds!!


EDIT: lol that link you sent me, he bought the same cords i showed above. thanks for that, now i wont have to wait to know they work :)
 
Computurd said:
@ stanza.
these devices are designed to be used this way.They arent some cheap little thing that isnt going to perform how they advertise it. They are guarantied for 5 years and unlimited writes. in single port mode you simply do not get the full performance.


snip
Click to expand...

Yes I did read what I could on their specs.... very nice.

Must have some interesting smarts inside to spread the reads n writes across the 3 x internal SSD's if thats the case.

Anyways ... looking at the specs and that page I linked to.

If / when you get them up and going.... one possible problem you might have to look into is the amount of IOPS your SAS cards can handle.

As that link stated they are what something like 160,000 IO/Sec yes?

And as he stated he had to get a SAS card that had 290,000 IO/Sec....

Which means if you plonk two of these on one SAS card, you are effectively choking them / limiting their performance?

Which then means you would virtually have to setup the system as 1 x HBA per Pliant Lightning LS 300S ??

So getting all 5 of them running full speed in one box should be interesting;)

Either way keep us informed of the outcome, good or bad as I am interested in the results.

.
 
this wont go badly.
I have a 9265 with fasptah that will push 465,000 IOPS, i already hit 420,000 IOPS with them in my enclosure, in single port mode. my enclosure is not dual port capable. well it is, but only for failover.
I also have a 1880IX-12 with 4gb cache, and a adaptec 6805 for this review.
so it will be fun. to say the least :)
i am going to connect the four devices in wideport to the expander ports on my enclosure, and use one inside the enclosure in single port mode.
so...it will be UBER. :) :)
 
Computurd said:
this wont go badly.
I have a 9265 with fasptah that will push 465,000 IOPS, i already hit 420,000 IOPS with them in my enclosure, in single port mode. my enclosure is not dual port capable. well it is, but only for failover.
I also have a 1880IX-12 with 4gb cache, and a adaptec 6805 for this review.
so it will be fun. to say the least :)
i am going to connect the four devices in wideport to the expander ports on my enclosure, and use one inside the enclosure in single port mode.
so...it will be UBER. :) :)
Click to expand...

Damn, that's like Quad SLI with dual GPU graphics cards, only with SSDs! :cool:
 
Last edited:
cool, now tell me which truck they fell off the back of.... so I can drive around following it..:D
 
it was a big truck that said PLAINT. LOL i would have to steal them myself, lucky they are on loan.
The 5 together are worth $35,000 USD.
and ups left them on the front porch! didnt even knock :)
 
Necro'ing this thread :) It's kinda confusing reading this - I'm still not 100% sure my requirement is the same as the OPs. Here's what I want: I am trying to set up and debug an active/passive HA cluster with two CentOS linux systems. Each one has an SAS HBA with at least one 7-pin sas/sata drive connector. I would like to connect the two HBAs to the two data ports on a spare 1TB SAS drive so I can experiment and get this all working before I deploy this on the production zfs pool. I found the following on amazon:

http://www.amazon.com/SAS-Hot-Swapp...sr=8-5&keywords=sas+backplane+to+signal+cable

this looks *exactly* like what I want, no? Each HBA will plug an sas/sata data cable into one of the two data ports, and a spare molex power connector on one of the hosts will power the adapter. Any reason this shouldn't work?
 
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